Aqueous coating compositions from chlorinated emulsifier-stabilized latex



Patented Dec. 22, 1953 AQUEOUS COATING COMPOSITIONS FROM CHLORINATEDEMULSIFIER-iS'l-ABILIZED L TEX Pe us H ve. i aastr ch N t n s assignorto lands Rubber-Stunting; Delft; Nether No Drawing. Application May 1!},1351),

Serial No. 1 3.0134

Claims priority, application Netherlands May 31, 1949 ,This inventionrelates to a process for manufacturing water impermeable films ofchlorinated rubber from aqueous dispersions thereof.

{The principal object of the present invention is to provide a simpleand reliable method for manufacturingimpermeable films of chlorinatedrubber. Another object of the invention is to manufacture an impermeablefilm of chlorinated rubber froman aqueous dispersion of chlorinatedrubber. A further object of the invention is to provide a method for themanufacturing of unsupported fil ns of chlorinated rubber. Still another object of the invention is to provide ,a method for manufacturingfilms of chlorinated rubber without using heatandpressure. Anotherobject of the invention is to provide a method for the production of anaqueous dispersion of chlorinated rubber from which can be producedanimpermeable self supporting film without the application ofsubnormalpressure. Other objects will'become apparent from the followingdescription.

It is known to produce films of chlorinated rubher from a solution ofchlorinated rubber in volatile solvents, if desired, mixed with aplasticizer. It isalso known to make an aqueous dispersion of ordinarychlorinated rubber anda plasticizer, from which aqueous dispersion adense film can, however, only be produced by the use of [hot calenders(Jr-stacks. The dry powder which re.- mains after the evaporation of thewater can only be fused into a coherent filmand, ifdesired, at the sametime welded to the base bysubjectin'g' the layer to a treatment byheated rolls.

In the operation of the process of the present invention impermeablefilms of chlorinated rub,-

her are manufactured by forming a thinlayer of an aqueous dispersion ofa mixture of aplasticizer and chlorinated rubber, which has beenproduced by chlorinating an acid-reacting aqueo'us dispersion ofunmasticated rubber and which has a chlorine content of at most '6l%,preferably'between55 and.60 evaporatingthe water from the thin layer ofthe dispersion andallowing the remaining plasticized chlorinated rubberto flow into a dense, homogeneous film without'the application ofpressure thereto. The evaporation ofthe water leaves numerousseparate'gl-obules of the solid ingredients of the dispersion.

I have discovered the remarkable fact that these separate globules mergeor coalesce into a clear, coherent, stron water impermeable film withoutapplying pressure, only whenthe chlorinated rubber and the plasticizenaswell astheir relative amounts in the aqueous dispersions,

A 40% emulsion of chlorinated rubber havin a chlorine contsi t of 57%was preparedby chlolinating latex, stabilized against acid coagulationby the presence'of 2% of Emulphor (an emulsifier sold by the General'Dyes'tuff Corp.

' and believed to be the reaction product polyethylene oxide witholeylalcohol) (calculated on the rubber) 'and'acidified withhydrochloric acid to a normality 8 and chlorinated until thedesired'chlorine contentwas obtained. The chlorinated rubber separated from thislatex by coagulation with alcohol was dispersed in a ball mill withwater and a'slight quantity of an emulsifier of the non-ionic type,consisting in the reaction product of polyethylene oxide with analkylated phenol. To this dispersion a 65% emulsion of dibutylsebacatewas added in a quantity of 20 parts of the plasticizer to 100 parts ofchlorinated rubber.

Theemulsion obtained was applied to a wooden surfaceby sprayingand gaveafter standing for about 60 minutes at room temperature a completelyhomogeneousand dense-film.

Another part of the wooden surface coated with the same aqueousdispersion of chlorinated rubber was exposed to infra-red radiation,whereby its temperature was increased to 50 to 60 0., in this case thefilm formation .was completed in less than 10 minutes.

.Asecond example of'the process of the present invention is given forthe production of a selfsupporting, transparent film of chlorinatedrubber.

The chlorinated rubber prepared as in Example 1 was dispersed in a ballmill with water and a slightquantity' of soap.

To this emulsion a emulsion or dibutylsebacate-Was-added in a quantityof 10 parts of the plasticizer to 100 parts of-chlorinatedrubber.

By spreading such an emulsion on a smooth metal band which may e. g.consist of aluminum or stainless steel, the desired film is obtained.Within a few minutes after heating at C. the film can be stripped offthe metal surface. i A--third example of the process of'thepr'esentinvention is given for the preparation of a ch10 rmated rubbercoatingmaterial to which apigment hasbeen added a 1 I s a filler. To adispersion of chlorinated rubber having a chlorine content of 58%produced as described in patent application Serial No. 775,155, filedSeptember 19, 1947, 100 parts by weight of titanium white and 30 partsby weight of chlorinated diphenyl were added per 100 parts by weight ofchlorinated rubber. The emulsion was spread on a-textile and by slightheating worked up to a flexible film which could be folded withoutshowing cracks and adheres tenaciously to the fabric.

A fourth example of the process of the present invention shows how thepermeability for water vapour of films containing a plasticizer in sucha large amount that they can be formed in a short time without heatingis favorably influenced by the further addition of a slight quantity ofa high molecular substance to the dispersion. Films prepared fromdispersions of the following composition (in parts by weight) werecompared.

it??? r Chlorinated rubber water Dibutyl- Added as aqueous aag sebacatedispersion 5 3i cmfimmJ- hour 25 6 X 25 2% rubber 2. 2 X 10- 25 10cyclized rubber--. 3. 3 X 10- 25 10 polyvinylchloride.- 4.2 X 10- Thechlorinated rubber which should be used in the process of the presentinvention is obtained by allowing chlorine to react with latex to whichso much acid has been added that an acid liquid with a normality of atleast 1 has been obtained and which latex has been stabilized beforehandin such a. manner that it does not coagulate by the said addition ofacid. This process for preparing aqueous chlorinated rubber dispersionsfree from organic solvents is more fully described in Patent No.2,586,124 and the thus obtained product is distinguished from thechlorinated rubber prepared in solution by the fact that the rubbermolecules have not been broken down.

The chlorinated rubber prepared according to the said patent isespecially distinguished from the chlorinated rubbers prepared by thechlorination of latex in other ways by very low oxygen content andmoreover by a somewhat lower chlorine content and by its insolubility inthe usual organic solvents for chlorinated rubber. Whereas it is generalpractice, when chlorinating rubber in solution, to obtain a chlorinatedrubber with approximately 65-68% of chlorine, it appears that thechlorination in' latex does not easily proceed further than a chlorinecontent of approximately 60%. Although this chlorinated rubber with arelatively low chlorine content has less favorable properties withrespect to the heat and light stability compared with the chlorinatedrubber prepared in solution, it appears that the lower softening pointrenders this chlorinated rubber excellently suitable for the applicationof the process of the present invention. An additional advantage of thechlorinated rubber prepared according to the process of the said patentis the insolubility which is caused by the fact that the rubbermolecules have not been broken down at all. It is known that rubberwhich has been separated from latex and thereupon masticated by rollers,owing to this treatment in the presence of oxygen has suffered adecomposition which decomposition deliberately is continued to a veryhigh degree when it is desired to prepare concentrated solutions ofrubber as applied in the manufacture of chlorinated rubber. Theinsolubility of the chlorinated rubber which is preferably usedaccording to the present invention renders an application of a packingmaterial treated with this chlorinated rubber poss'ible when packingoils, fats and the like products which would in the long run dissolve afurther broken down chlorinated rubber.

The preparation of an aqueous dispersion of the chlorinated rubber usedin the process of the present invention iseasily accomplished by simplymilling the precipitated and washed chlorinated rubber with a suitableamount of water and a suitable emulsifying agent in a ball mill. Otherdevices, as used in the paint industry e. g. a colloid mill can be used.

As an emulsifier for the preparation of the dispersion of chlorinatedrubber and plasticizer one of the numerous substances which are on themarket for this purpose can be used, such as sulphonated oils orhydrocarbons, cationic or invert soaps, non-ionic emulsifiers and alsonatural products such as casein. I prefer to use an emulsifying agentwhich will give a stable suspension when used in an amount between 1-5%calculated on chlorinated rubber. The plasticizer exerts a gellingaction on the chlorinated rubber. To obtain clear coherent films in areasonable time, it is necessary to use a fairly large amount ofplasticizer, which should, however, be sufliciently miscible with thechlorinated rubber. Some suitable plasticizers are dibutylsebacate,tricresylphosphate, dibutylphthalate, dioctylphthalate, dioctylsebacate,butyloleate.

These plasticizers can be used together with other substances which mayexert less plasticizing action when used alone or which may not besufficiently compatible with the chlorinated rubber when used without amutual solvent plasticizer. Examples of such substances, givingexcellent films when used together with dibutylsebacate ordibutylphthalate are parafiin oil and other mineral oils. Thesesubstances tend to make the film more stretchable and elastic. When lesselastic properties are desired, aqueous dispersions of cyclized rubberor of polyvinylchloride can be added to the chlorinated rubberdispersion. The cyclized rubber is preferably prepared by cyclizing astabilized natural rubber latex, prepared according to the processdescribed and claimed in the copending application Serial No. 59,190,filed November 9, 1948, now U. S. Patent 2,555,068, which process leadsto the formation of an aqueous dispersion of cyclized rubber havingparticles of about the same size as the original rubber latex. Thepolyvinylchloride should be prepared by emulsion polymerisation and ispreferably used as the dispersion resulting therefrom. An aqueousdispersion of a natural or synthetic rubberlike material can also beadded to the aqueous dispersion of the chlorinated rubber, whereby theimpermeability of the finally obtained film can be greatly improved.Examples of suitable rubberlike materials are Hevea-rubber, "neoprene (apolymer of 2-chlorobutadiene) GRr-A (a copolymer of butadiene andacrylonitrile) and GR S (a copolymer of butadiene and styrene). Theserubbers are at present available as aqueous dispersions. Relativelyextensible, transparent films can be produced by using from 2 to 20% ofthe rubberlike substance calculated on the chlorinated rubber.

The film formation without pressure and at debate? 5 room temperatureproceeds more easily when the amount of plasticizers is "increased andwhen the chlorinated rubber used *has a lower chlorine content.

The quantity of added plasticizer can range from 10 to 35%-"(cal'culated "on the amount of chlorinated rubber). The amount ofplasticizer has a great influence on the quality of the film e. g. theelasticity and the stickiness. An amount of plasticizer exceeding 35%gives aifilm having a stickiness too hig-h for practical uses. Very goodelastic qualities are obtained by films containing 1 5 to 25% ofplasticizer. Starting from a chlorinated rubber with higher chlorinecontent more plasticizer has to be added than when a chlorinated rubberwith a lower chlorine content is used as a starting material. Thecomposition of two emulsions from which chlorinated rubber films can bemanuf aotured starting from -the same chlorinated rubber (with 150% C1)but which emulsions contain different percentages of chlorinated rubberand which content is given in schedule here below.

I II

Percent Percent Chlorinated rubber 25 45 Dibutylsebacate 7. 5 10Emulphor O 0. 5 0. 5 Water 67. 44.

Chlorinated rubber having a chlorine content of from Parts by weight50-60% by weight 25 45 Dibutylsebacate 1.5 -16 Emulsifying agent 0.25-2.2 Water to make up 100 Dibutylsebacate is especially suitable as aplasticizer in the process according to the present invention but alsoother esters of sebacic acid and of phthalic acid and of phosphoric acidcome into consideration as well as chlorinated diphenyl. With the lastmentioned plasticizer a non-adhering film can only be obtained withdiificulty; this renders this kind of plasticizer less suitable for theproduction of self-supporting films, but particularly suitable for theapplication in films which should strongly adhere to the base.

In general heating to a temperature between 40 and 60 C. will besufficient for the film formation to take place in a few minutes. Theheating can, however, be increased without drawback to a little below100 C. in which case the film formation takes place in a still shortertime; but no further advantages are obtained, A film can also beobtained without an heating in which case, however, a longer period oftime is necessary, which appears to be due almost entirely to the slowerevaporation of the water.

An important application of the films combined 7 with paper or cardboardaccording to the present invention consists in their use for packingmaterial. The decreased stability to light cannot produce a disadvantagewhen care is taken that the 6 film is protected against light by thepaperlayen Since-in this manner also the paper or cardboard isprotectedagainst attack, if any, by ingredients in the packed substances, in thismanner a-simple and efficient packing material is found for substanceswhich so far could only be packed in :tins or the like hermeticallysealed materials.

The'stab'ility of the films of chlorinated rubber obtained with respectto heat and lightcanbe im-' proved by adding in some stageofth'e'preparation substances which already in small quantities have afavorable influenc on the stability, such :aseg. amines or metal oxides.

The permeability for water vapour of the films obtained depends on thethickness and on the quantity and kind of the plasticizer used. :Inafilm containing '10 parts of dibutylsebacate per 100 parts ofchlorinated rubber and having :a thickness of 1092-0503 mm. apermeability-for water vapor of approximately 0.7 to 015x101? g. cm/cm?.mm./hour can be obtained.

Lolaim:

51.;In the manufacture of water-impermeable films of rubber chloride,the process which comprises .fforming such .affilm'from a coating.composition consisting substantially of an aqueous dispersion, freefrom organic solvents, of from about 25 to 45 per cent by weight of afinely-divided rubber chloride having a chlorine content of from about50 to 60 per cent by weight and being substantially free from oxygen andsubstantially insoluble in organic solvents; and of from about 10 to percent by weight, based on the weight of the rubber chloride, of aplasticizer which is miscible with the rubber chloride and exerts agelling action thereon; and evaporating the water from said film thuscausing the dispersed, plasticized chlorinated rubber to coalesce intoan impermeable homogeneous film without heating above about 100 C. andwithout the application of pressure; said finely-divided chlorinatedrubber resulting from the chlorination of an aqueous dispersion of anunmasticated rubber containing acid in a concentration of at least about1 normal and an emulsifier stabilizing it against acid coagulation.

2. The process of claim 1 wherein said aqueous dispersion contains fromabout 0.25 to 2.2 per cent of an emulsifying agent.

3. The process of claim 1 wherein said film is formed by applying thesaid aqueous dispersion to a smooth surface, followed by evaporation ofthe water therefrom and then stripping the film from the surface to forma self-supporting film.

4. The process of claim 1 wherein said film is formed by applying thesaid aqueous dispersion to paper and cardboard whereby upon evaporationof the water therefrom a firmly adherent water-impermeable film'isformed, the product being suitable for use as a packing material.

5. The process of claim 1 wherein water is evaporated from said film byheating it to a temperature below 100 C.

6. The process of claim 5 wherein the heating is produced by exposingthe film to infra-red radiation.

7. A coating composition consisting substantially of from about 25 toper cent by weight of a chlorinated rubber, having a chlorine contentwithin the range of from about to per cent by weight, from about 10 to35 per cent by weight, based on the weight of the chlorinated rubber, ofa plasticizer which is miscible with the rubber chloride and exerts a,gelling action thereon, a small amount of a compatible emulsifier and avehicle of water; the rubber chloride insaid composition beingsubstantially free from oxygen, being substantially insoluble in organicsolvents and resulting from the chlorination of an aqueous dispersion ofan unmasticated rubber containing acid in a concentration of at leastabout 1 normal and an emulsifier stabilizing it against acid coagulationfollowed by recovery of the finely-divided chlorinated rubber from theresulting chlorinated dispersion.

8. In the manufacture of water-impermeable films of chlorinated rubber,the process which comprises forming such a film from an aqueousdispersion containing from about to parts by weight of a finely-dividedchlorinated rubber having a chlorine content of from about to per centby weight and being substantially free from oxygen and substantiallyinsoluble in organic solvents, from about 0.25 to 2.2 parts by weight ofemulsifying agent and from about 1.5 to 16 parts by weight of dibutylsebacate, the water present being sufiicient to make a total of 1 00parts by weight; and evaporating the water from said film therebycausing the dispersed particles of rubber chloride to coalesce into animpermeable continuous film without heating above about C. and withoutapplying pressure; the rubber chlo ride in said aqueous dispersionresulting from the chlorination of an aqueous dispersion of anunmasticated rubber containing acid in a concentration of at least 1normal and an emulsifier stabilizing it against acid coagulation.

PETRUS TEN HAVE.

References Cited in the file of this patent UNITED STATES PATENTS NumberName 7 Date 2,008,558 Laufenberg July 16, 1935 2,161,454 Calvert June 6,1939 2,333,258? Redlinger Nov. 9, 1943 2,374,759 Latour May 1, 19452,416,447 Laughlin et a1 Feb. 25, 1947 2,423,555 Ender July 8, 19472,536,789 Van Amerongen Jan. 2, 1951 2,586,124 Van Amerongen Feb. 19,1952 FOREIGN PATENTS Number Country Date 418,068 Great Britain Oct. 18,1934 634,241

Great Britain Mar. 15, 1950

7. A COATING COMPOSITION CONSISTING SUBSTANTIALLY OF FROM ABOUT 25 TO 45PER CENT BY WEIGHT OF A CHLORINATED RUBBER, HAVING A CHLORINE CONTENTWITHIN THE RANGE OF FROM ABOUT 50 TO 60 PER CENT BY WEIGHT, FRO ABOUT 10TO 35 PER CENT BY WEIGHT, BASED ON THE WEIGHT OF THE CHLORINATED RUBBER,OF A PLASTICIZER WHICH IS MISCIBLE WITH THE RUBBER CHLORIDE AND EXERTS AGELLING ACTION THEREON, A SMALL AMOUNT OF A COMPATIBLE EMULSIFIER AND AVEHICLE OF WATER; THE RUBBER CHLORIDE IN SAID COMPOSITION BEINGSUBSTANTIALLY FREE FROM OXYGEN, BEING SUBSTANTIALLY INSOLUBLE IN ORGANICSOLVENTS AND RESULTING FROM THE CHLORINATION OF AN AQUEOUS DISPERSION OFAN UMASTICATED RUBBER CONTAINING ACID IN A CONCENTRATION OF AT LEASTABOUT 1 NORMAL AND AN EMULSIFIER STABILIZING IT AGAINST ACID COAGULATIONFOLLOWED BY RECOVERY OF THE FINELY-DIVIDED CHLORINATED RUBBER FROM THERESULTING CHLORINATED DISPERSION.